Methods and devices for delivering occlusion elements

ABSTRACT

A device for delivering an occlusion element, or other medical device, which includes a fluid dissolvable bond. The occlusion element is coupled to the delivery element with the fluid dissolvable bond. The bond may be dissolved by delivering a fluid through the delivery element either through the delivery element itself or through a tube positioned in the delivery element.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of Methods and Devicesfor Delivering Occlusion Elements, Ser. No. 09/780,587, filed Feb. 9,2001, the full disclosures of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to the delivery of medical devices and, inparticular, occlusion elements. Occlusion elements, such as coils, aredelivered to occlude vascular regions and malformations for variousreasons. For example, occlusion elements, such as coils, may bedelivered into an aneurysm to occlude the aneurysm. Other uses ofocclusion elements include treatment of AVM's and other malformations.

SUMMARY OF THE INVENTION

The medical device, such as the occlusion element, is coupled to adelivery element with a material which is dissolvable with a fluid. Thematerial forms a dissolvable connection between the delivery element andthe occlusion element. The occlusion element is advanced through thepatient's vascular system and, at the appropriate time, the material isdissolved. The dissolvable material is preferably dissolved with a fluidwhich is delivered to the material through the delivery element orthrough a tube positioned in the delivery element. The fluid may bedelivered, withdrawn or otherwise circulated around the material withthe tube and delivery element in any suitable manner. Alternatively, thematerial may be dissolved with the patient's own blood. Finally, thefluid may also be contained within the delivery element but separatedfrom the material until the desired time. Although the present inventionprovides a few exemplary fluids and dissolvable materials, the fluid anddissolvable material combination may be any suitable combination withoutdeparting from the scope of the invention.

The occlusion element may be embedded in the material. For example, theocclusion element may have a coil, a plurality of filaments, a ball or acage embedded in the material. The embedded portion may also be in abiased position, either expanded or collapsed, when embedded in thematerial. In this manner, the embedded portion helps to mechanicallydisturb the dissolvable portion to release the device as the materialdissolves. For example, the embedded portion may be a stacked coil whichexpands when released. The delivery element itself may also have aportion embedded in the material, such as a number of filaments, tofurther secure the delivery device to the occlusion element.

A blocking element may also be provided which protects part of thedissolvable material from exposure to blood or other fluids. Theblocking element may be positioned within a cavity in the material. Thecavity may be a throughhole through which the fluid is delivered whendissolving the material. The blocking element may also help to protectthe connection from kinking and other mechanical disturbances whichoccur when advancing the occlusion element through small, tortuousvessels. The blocking element can prevent inadvertent mechanicaldetachment when the device is bent or otherwise deformed duringadvancement through the patient. The occlusion element itself may alsohave a blocking portion which prevents contact between the patient'sblood and the material thereby inhibiting premature dissolution of thematerial. The blocking portion may be a plug of material such as solder.

A flexible sheath may also be positioned over the material to protectthe material. The sheath may be solid or may have openings or slitstherein to promote flow through the sheath when dissolving the material.The delivery element may also have a fluid distributing portion whichdistributes the fluid for dissolution of the material.

These and other advantages of the invention will become apparent fromthe following description of the preferred embodiments, claims anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a system of the present invention.

FIG. 2 shows an occlusion element.

FIG. 3 shows the occlusion element mounted to a delivery element.

FIG. 4 shows the distal end of the delivery element with a blockingelement removed from a cavity in the dissolvable material.

FIG. 5 shows the distal end of the delivery element with the dissolvablematerial dissolved and the occlusion element released.

FIG. 6 shows another device for delivering the occlusion element.

FIG. 7 shows the device of FIG. 6 after partial dissolution of thematerial.

FIG. 8 shows the occlusion element released from the delivery device.

FIG. 9 shows still another device for delivering an occlusion element.

FIG. 10 shows the occlusion element of FIG. 10 released from thedelivery element.

FIG. 11 shows yet another device for delivering an occlusion element.

FIG. 12 shows the occlusion element of FIG. 11 released from thedelivery element.

FIG. 13 shows yet another device for delivering an occlusion element.

FIG. 14 shows the occlusion element of FIG. 13 released from thedelivery element.

FIG. 15 shows another device for delivering an occlusion element withthe occlusion element inhibiting fluid contact with the material.

FIG. 16 shows the occlusion element of FIG. 16 released from thedelivery element.

FIG. 17 shows still another device for delivering an occluding element.

FIG. 18 shows the occlusion element of FIG. 17 released from thedelivery element.

FIG. 19 shows still another device for delivering an occluding element.

FIG. 20 shows the occlusion element of FIG. 19 released from thedelivery element.

FIG. 21 shows another device for delivering the occluding element.

FIG. 22 shows the device of FIG. 21 with the material partiallydissolved.

FIG. 23 shows the device of FIGS. 21 and 22 with the material dissolvedto release the occlusion element.

FIG. 24 shows the occluding element mounted over another deliveryelement with the delivery element having a coil.

FIG. 25 shows another delivery device having a textured surface overwhich the dissolvable material is mounted.

FIG. 26 shows the delivery element having a preloaded portion whichexerts a releasing force on the occlusion element.

FIG. 27 shows the occlusion element released.

FIG. 28 shows the occlusion element having a preloaded portion embeddedin the material.

FIG. 29 shows the material dissolved and the occlusion element released.

FIG. 30 shows a heating element which is used to heat the material toaid in dissolution of the material.

FIG. 31 shows another system for delivering the occlusion element.

FIG. 32 shows the system of FIG. 31 with a tube retracted to expose thematerial.

FIG. 33 shows a system for delivering a number of occlusion elements.

FIG. 34 is a cross-sectional view of the system of FIG. 33 along lineI-I.

FIG. 35 shows another system for use with the devices and methods of thepresent invention.

FIG. 36 shows another multiple element delivery system.

FIG. 37 shows still another system for delivering a medical device, suchas the occlusion element, with a threaded portion embedded in thedissolvable material.

FIG. 38 shows the material dissolved and the threaded portion released.

FIG. 39 shows another system for delivering an occlusion element whichhas preloaded portion embedded in the dissolvable material.

FIG. 40 shows the preloaded portion released.

FIG. 41 shows another system for delivering the occlusion element.

FIG. 42 shows the system of FIG. 41 with the occlusion element released.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-4, a system 2 for delivering a medical device 4,such as an occlusion element 6, is shown. The invention is described inconnection with delivery of the occlusion element 6, however, thedevices and methods of the present invention may be used to deliver anyother medical device to any part of the body without departing from thescope of the invention. The system 2 includes a delivery element 8 towhich the occlusion element 6 is mounted. A fluid dissolvable material10 forms a dissolvable connection between the occlusion element 6 andthe delivery element 8. For example, the material may be a sugar (suchas mannitol), salt or combination thereof or the material may be apolymer which is dissolved with a fluid having a specific pH range.These and other examples and combinations of fluid and dissolvablematerial 10 are provided below. The material 10 and fluid used todissolve the material 10 may be any suitable combination and numerouscombinations not described herein may be used without departing from thescope of the invention.

The occlusion element 6 is shown as a short section of coil for claritybut may be any suitable occlusion element 6 such as those described inU.S. Pat. Nos. 5,855,578, 5,853,418, 5,749,894 and 5,749,891 which arehereby incorporated by reference. In the preferred embodiment, theocclusion element 6 is made of platinum wire or ribbon which forms coils7. Of course, any suitable materials and structure may be used to formthe occlusion element 6. The delivery element 8 is preferably a tube 11having at least one lumen 12, however, the delivery element 8 may alsobe a solid element such as a wire or mandrel without departing from thescope of the invention. The occlusion element 6 is mounted to the end ofthe delivery element 8 and extends from the delivery element.

The system 2 of FIG. 1 shows delivery of the occlusion element 6 to thecerebral vasculature, however, the system, devices and methods of thepresent invention may be used to deliver the occlusion element 6, orother medical device, to any location in the patient. The system 2includes a guide catheter 5 which is advanced to a suitable location. Amicrocatheter or sheath 12 may then be advanced through the guidecatheter 5. The delivery element 8 is then advanced through themicrocatheter 12 to the desired release site. The microcatheter orsheath 12 may hold the occlusion element 6 in a collapsed condition asdemonstrated in the patents incorporated by reference above. The element6 forms the coiled structure of FIG. 2 as it exits the distal end of thesheath 12. The delivery element 8 may receive a blocking element 14which is described in further detail below. A fluid circulating device15, such as a source of fluid 16, is coupled to the delivery element 8for delivery of the fluid that dissolves the material 10. The fluid maybe any suitable fluid such as saline but may also be the patient's ownblood, a mixture of saline and contrast to visualize the area or anycombination thereof.

The occlusion element 6 is mounted to the delivery element 8 with thefluid dissolvable material 10 which forms a dissolvable bond orconnection 11. The fluid is preferably delivered to the dissolvablematerial 10 from the source of fluid 16 so that the dissolution of thematerial 10 may be controlled by delivery of the fluid. Although it ispreferred to deliver the fluid to dissolve the material 10, however, thefluid may also simply be the patient's own blood. Such a device may bepracticed with various aspects of the invention described herein withoutdeparting from the scope of the invention.

The fluid may simply erode or dissolve the bond 12 or the material 10may be dissolved with additional chemical, thermal or mechanical action.For example, the fluid may be an acid, base or other ionic fluid whichchemically dissolves the material 10. For example, hydrogen chloride maybe used to dissolve a connection having zinc or hydrogen peroxide may beused to dissolve a connection having iron. The fluid 16 and material 10may also form a solvent/solute relationship such as Hypan dissolved by afluid such as dimethyl sulfoxide.

In still another example, the material 10 may be a cross-linked polymersuch as a cross-linked alginate. The alginate may dissolve in thepresence of a suitable fluid containing a monovalent, divalent, ortrivalent cation such as saline. The alginate may be cross-linked in anysuitable manner such as with calcium chloride.

In still another example, the material may be a polymer whichpreferentially dissolves upon a pH or salinity change or uponapplication of an electric field. Such a polymer is sold under the tradename EUDRAGIT® by Rohm GmbH of Darmstadt, Germany, which is an acrylicpolymer and more specifically a methacrylate polymer. The polymercompound has polymer layers bonded together with hydrogen bonds inalternating layers of positive and negative charge. The bond between thepolymer layers is broken by application of the pH or salinity change orupon application of an electric field. For example, the fluid 16 mayalso have a pH which dissolves the material 10 faster than the pH ofother fluids which the material 10 is exposed to. Thus, if the material10 is exposed to blood, saline, contrast and the like, the dissolvablematerial 10 is preferably selected to at least dissolve slowly, if atall, at the pH of these fluids and more quickly when exposed to theappropriate pH fluid. In a preferred embodiment, the material dissolvesat least three times faster, and more preferably at least five timesfaster at the selected pH than at the pH of other fluids to which it isexposed. The dissolution rate can also be enhanced by flowing fluid intocontact with the dissolvable material.

Once the occlusion element is at the desired location, a fluid, such assodium bicarbonate, having the appropriate pH is delivered to dissolvethe material 10. As mentioned above, the material 10 may dissolve slowlyin the fluids to which it is exposed so long as the material dissolvesfaster when exposed to the appropriate fluid. EUDRAGIT®, for example,dissolves slowly in blood or saline, however, the polymer dissolves muchfaster with the appropriate fluid. In a preferred embodiment, the fluidhas a pH of either about 4-6 or about 8-9.5.

In a specific example, EUDRAGIT® L100 and S100 (1:1) are dissolved withan ethyl alcohol/water (95:5 by weight) solvent at a ratio of 0.05 GEUDRAGIT® per gram of solution using a magnetic mixer. Small drops ofthe EUDRAGIT® solution are then applied to the appropriate area betweenthe medical device or element and the delivery or insertion element. Thedrop is then dried which may take 1-5 hours during which time thesolvent substantially evaporates leaving the EUDRAGIT® material to formthe dissolvable bond. If necessary or desired, additional drops orcoatings may be applied after the previous drop, coating or applicationhas dried.

Thus, it can be appreciated from the various examples provided abovethat a number of different combinations of fluid and dissolvablematerial may be used and numerous other combinations are possiblewithout departing from the invention.

Referring again to FIG. 3, the blocking element 14 may be used toprotect parts of the dissolvable material 10 during introduction andadvancement of the occlusion element 6. The blocking element 14 maysimply be a wire, guidewire, mandrel or even a tube. The blockingelement 14 may be positioned adjacent or against any portion of thematerial 10 and is preferably positioned in a cavity 18 in the material10. The cavity 18 is shown as a throughhole 20 but may take any othershape such as a hole closed on one end. The blocking element 14temporarily blocks the cavity 18 to inhibit dissolution of the material10. When the blocking element 14 is withdrawn, part of the material 10is exposed thereby permitting dissolution of the material 10. Of course,fluid may be in contact with the material 10 even with the blockingelement 14 positioned in the cavity, however, the blocking element 14will at least inhibit fluid flow around the dissolvable material 10thereby preventing premature dissolution of a substantial portion of thematerial 10.

The delivery element 8 may include a sheath 22 extending over an outersurface of the dissolvable material 10. The sheath 22 protects the outersurface of the material 10 to inhibit dissolution of the material 10.The sheath 22 may be any suitable flexible sheath and may be made of anysuitable material such as PET. The delivery element 8 has a coil 24coupled to a tube 26. The coil 24 provides a flexible distal end foradvancement of the delivery element 8 through tortuous vessels. Thesheath 22 may extend over the coil 24 and tube 26 or only over a portionof the coil 24 and material 10.

Referring to FIGS. 6-8, another device for delivering the occlusionelement 6 is shown wherein the same or similar reference numbers referto the same or similar structure. The delivery element 8A has openings28 therein through which fluid is delivered when dissolving the material10. The openings 28 may be in the sheath 22A extending over the material10. The openings 28 may also be one or more slits 30 in the sheath 22Awhich open when positive pressure is applied so that the slit 30 acts asa valve which opens when the fluid is delivered yet covers the material10 during introduction and advancement. The openings 28 may also be partof a portion 32 of the delivery element 8 that extends into the material10. The portion 32 extending into the material 10 may, for example, be aconical section 34. The openings 28 serve as fluid channels whendissolving the material 10 so that the material 10 may be dissolvedrelatively quickly at the desired time. An advantage of such a design isthat the dissolvable material 10 may be kept relatively robust whilemaintaining the ability to quickly dissolve the bond at the appropriatetime. Use of the blocking element 14 (FIG. 2) further enhances theability to control dissolution of the dissolvable material 10 asdiscussed above and specifically incorporated here.

Referring to FIGS. 9 and 10, still another device for delivering anocclusion element 6B is shown wherein the same or similar referencenumbers refer to the same or similar structure. The occlusion element 6Bhas a portion 40 embedded in the dissolvable material 10. The portion 40is preferably naturally biased toward the collapsed position of FIG. 10when released. The dissolvable material 10 is shown as a solid plug ofmaterial 10 but may, of course, have the cavity or throughhole as shownin connection with FIGS. 3-8 without departing from the scope of theinvention. A tube 42 delivers, withdraws or otherwise circulates thefluid to dissolve the material 10 at the desired time. The tube 42 andlumen 12 in the delivery element 8 are coupled to the fluid circulatingdevices 15. The fluid circulating devices 15 may be either the fluidsource 16 with pump or a fluid withdrawal device 17, such as a vacuumsource or vacuum pump, which are used to circulate the fluid around thematerial 10. For example, the fluid may be delivered through either thetube 42 or through the annular area between the delivery element 8 andtube 42 with the other element being used to withdraw the fluid.Alternatively, the tube 42 may be used with the fluid withdrawal device17 to withdraw fluid into the tube 42 while drawing the fluid throughthe lumen 12. Of course, the fluid may also be simply pulsed one way andthen the other so long as the fluid is generally being circulatedthrough the area to dissolve the material 10. One advantage of such assystem is that the dissolved material 10 may be withdrawn through thedelivery element 8 or tube 42.

The tube 42 and annular area between the delivery element 8 and tube 42may also be used to prime the device with a suitable fluid. The primingfluid may be a fluid which does not dissolve the material 10 or whichdissolves the material 10 very slowly. The tube 42 and annular areabetween the delivery element 8 and tube 42 may also be used to activelyremove air as well as for delivery of the fluid after advancing thedevice to the desired release site. Although the devices describedherein include a separate tube 42, the device 8 may also simply have twolumens instead of the tube 42 without departing from the scope of theinvention.

Referring to FIGS. 11 and 12, yet another device for delivering anocclusion element 6C is shown wherein the same or similar referencenumbers refer to the same or similar structure. The occlusion element 6Chas a plurality of filaments 44 embedded in the dissolvable material 10.The tube 42 may be used to circulate the fluid and dissolve the material10 at the desired time. Referring to FIGS. 13 and 14, still anotherdevice 8D for delivering an occlusion element 6D is shown wherein thesame or similar reference numbers refer to the same or similarstructure. The delivery element 8D has a plurality of filaments 44embedded in the dissolvable material 10. An advantage of the device 8Dis that the filaments 44 are not part of the occlusion element 6D sothat the occlusion element 6C may be substantially a conventionalocclusion element 6D. The occlusion element 6D also has a distal block46, which inhibits, and preferably prevents, fluid from entering thedistal end of the delivery element 8 to protect the dissolvable material10 from exposure to blood. The distal block 46 is preferably solder 48but may be any other suitable material 10.

Referring to FIGS. 15 and 16, yet another device for delivering anocclusion element 6E is shown. The occlusion element 6E has a blockingelement 50, which is preferably a first disc 52, which prevents exposureof the material 10 to blood. A second disc 54, or other suitable shape,anchors the occlusion element 6 to the material 10. A third disc 56serves to move the coil out of the delivery element 8 after melting ofthe dissolvable material 10. The pressure of the fluid is increased sothat the pressure forces on the third disc 56 push the occlusion element6E out of the delivery element 8. The third disc 56, of course, does notcompletely prevent proximal exposure of the dissolvable material 10since the fluid is delivered through the delivery element 8, preferablywith the tube, to melt the dissolvable material 10.

Referring to FIGS. 17 and 18, another occlusion element 6F is shown. Theocclusion element 6F has a ball 58, preferably 0.005-0.020 in diameter,embedded in the material 10. The ball 58 is attached to the rest of theocclusion element 6F with solder 60 which also serves as a blockingelement 63 to prevent distal exposure of the dissolvable material 10.Referring to FIGS. 19 and 20 still another occlusion element 6G is shownwhich has a cage 62 embedded in the material 10. The cage 62 is attachedto the rest of the occlusion element 6 with solder 60 which also servesas the blocking element 63 to prevent distal exposure of the dissolvablematerial 10.

A method of delivering a medical device, such as an occlusion element 6,is now described in connection with the preferred embodiments, however,it is understood that the method may be practiced with any suitabledevice. As mentioned above, the invention may be used in any location inthe patient's body and use in the cerebral vasculature is described as aparticular use of the invention although any other medical device may bedelivered to any other part of the body for any other purpose. The guidecatheter 5 is introduced into a vessel, such as the femoral artery, andadvanced to a suitable location. The microcatheter 12 is then advancedthrough the guide catheter 5 to a location near the desired site forreleasing the occlusion element 6. The invention may be practiced withfewer or more delivery catheters, cannulae or sheaths without departingfrom the scope of the invention.

The occlusion element 6 is delivered to the desired location bymanipulating the delivery element 8. At the desired release time andlocation, the blocking element (FIG. 2), if used, may be moved to exposeat least part of the dissolvable material 10. Fluid is then deliveredwith the delivery element 8 and/or tube 42 to dissolve the material 10and release the occlusion element 6. Depending upon the particularembodiment, the release of the occlusion element from the dissolvablebond may completely release the occlusion element 6 from the deliveryelement 8 or the delivery element 8 may need to be withdrawn tocompletely release the occlusion element 6. An advantage of requiringadditional withdrawal of the delivery element is that the occlusionelement 6 may still be manipulated to some degree after release from thedissolvable bond. For example, the delivery element 8 may be advancedand manipulated further to move the occlusion element 6 afterdissolution of the material 10.

Referring to FIGS. 21-23, another device 64 for delivering the occlusionelement 6 is shown. The device 64 includes the dissolvable material 10that dissolves upon application of the fluid 16. As with all of theembodiments described herein, the material 10 and fluid 16 may be any ofthose described herein or any other suitable combination. The element 6is mounted to the delivery element 8 which may be a wire 66. The device64 is advanced through a catheter 68 such as the microcatheter or sheath12. The device 64 is advanced through a lumen 70 in the catheter 68 and,at the desired time, the fluid 16 is delivered through the lumen 70 todissolve the material 10. The lumen 70 may be filled or prepped with afluid which does not dissolve the material 10 during loading andadvancement of the element 6 through the catheter 12. For example, thedevice 64 may be prepped with saline and the fluid used to dissolve thematerial 10 may utilize a change in pH as described above. FIG. 22 showsthe dissolvable material partially dissolved and FIG. 23 shows theelement 6 released from the device.

Referring to FIGS. 24 and 25, another device 72 for delivering theocclusion element 6 is shown. Similar to the device of FIGS. 21-23, thedissolvable material 10 is dissolved with the fluid delivered throughthe lumen 70 in the catheter 12. The insertion element 8 may havefeatures which enhance the bond between the insertion element 8 andmaterial 10. For example, a helical wire or ribbon 73 can be wrappedaround the insertion element 8 (FIG. 24) or the surface of the insertionelement may be roughened or textured (FIG. 25) to enhance engagementwith the dissolvable material 10.

Referring to FIGS. 26 and 27, the devices described herein may also havefeatures which promote detachment of the element 6 from the insertionelement 8. For example, the insertion element 8 may exert a force on theocclusion element 6 which helps to detach the occlusion element 6. Thepre-loaded force may be imparted in any suitable manner such as with aspring 74. The spring 74 is compressed in the loaded position of FIG.26. As the material dissolves in the fluid, the spring 74 helps tomechanically disturb the dissolvable material 10 and also tends to forcethe element 6 away from the insertion element 8. FIG. 27 shows thespring 74 extended after detachment of the occlusion element 6. Thespring 74 may be radiopaque so that expansion of the spring may bevisualized to monitor release of the device or element.

Referring to FIGS. 28 and 29, the element 6 itself may be pre-loaded toexert forces on the dissolvable material. Proximal windings 76 of thecoil 78 can be stretched or compressed to pre-load the windings 76 whichare then embedded in the dissolvable material 10. In this manner, thewindings 76 themselves act to mechanically disturb the material 10thereby promoting detachment of the element 6. Pre-loading of theelement 6 may be used with any of the embodiments described herein (suchas FIG. 9) or other suitable structures.

Referring to FIG. 30, another device 79 for delivering the medicaldevice, such as the occlusion element 6, is shown. The device 79 alsohas the fluid dissolvable material 10 that is dissolved to release theelement 6. Similar to the use of a pH change to enhance dissolution, thematerial 10 may dissolve at a faster rate at a selected temperature. Thetemperature may be changed by simply heating or cooling the fluid or byheating the material 10 itself. The fluid may be heated and cooled withthe fluid circulating device 15 or with an element mounted to the deviceitself. For example, a heating element 80, which may use simpleresistive heating, may be mounted to the device or delivered through alumen in the device to heat the material 10. Referring to FIG. 30, theheating element directly contacts the material 10 to heat the material10.

Referring to FIGS. 31 and 32, another blocking element 82 is shown whichprotects the dissolvable material 10. The blocking element 82 is a tube84 that covers an interior surface 86 of the material 10. An outer tube85 covers the outer surface of the material 10. The blocking element 82is retracted to expose an inner tube 88 having openings 90 therein whichpermit fluid to contact the material 10 as shown in FIG. 32. The innertube 88 may also be retracted to further expose the dissolvable materialor the inner tube 88 may be omitted altogether. The fluid is deliveredthrough a lumen 92 to dissolve the material 10.

The present invention may also be used to deliver a number of elements 6with the same delivery element 94. Referring to FIGS. 33 and 34, anumber of the elements 6 are mounted to the insertion element 94 whichmay be a tube, shaft, wire or mandrel. The elements 6 are coupled to oneanother with the dissolvable material 10 to form a dissolvableconnection between each of the elements. Two lumens 96, 98 are formedbetween inner and outer tubes 100, 102 with the fluid being deliveredthrough one of the lumens 96 and withdrawn through the other lumen 98(FIG. 34). The fluid passes through openings 104 in the inner tube 100and into contact with the dissolvable material 10. The fluid, togetherwith the dissolved material 10, is then withdrawn through openings 106in the other side of the inner tube 100 and out through the other lumen98. After the occlusion element 6 has been released, the deliveryelement 94 is advanced to position another of the dissolvableconnections between the openings 104, 106 to dissolve anotherconnection. This process is repeated until all of the occlusion elements6, or a desired number, have been released.

Referring to FIG. 35, a system 110 for flushing the device with aflushing fluid 112 is shown. The flushing fluid 112 is delivered toeliminate the fluid 114 used to dissolve the material 10. Flushing thesystem is particularly useful when delivering a number of elements 6with the same delivery device to prevent premature release ordegradation of the dissolvable connections. The flushing fluid 112 andfluid 114 used to dissolve the material may be coupled to a fluidcontrol system 116 that controls delivery of the two fluids. The fluidcontrol system 116 may include a detector 1 18, described below, whichdetects when an element 6 has been released so that the flushing fluid 112 can then be delivered. When the user desires to deliver anotherelement 6, the user prompts the system to switch back to delivery of thefluid 114 which dissolves the material for release of another element 6.

As mentioned above, the detector 118 is particularly useful with themultiple element system described above but may be used to simply alertthe user when the element 6 has been detached so that the usermanipulates the insertion element appropriately once detachment hasoccurred. Detecting detachment of the element 6 may also be used todetermine when to flush the system with the flushing fluid 112. Onemethod of detecting detachment is to apply energy to the device anddetect a change in a measured parameter or characteristic of the energy.For example, the detector 118 may apply a low power RF signal with thestanding wave ratio (SWR) being measured. The SWR will change when theelement 6 has been released so long as an appropriate frequency and/orwavelength is selected. Other types of energy, such as electricalenergy, may be used while measuring other parameters, such as electricalresistance, without departing from the scope of the invention.

Referring to FIG. 36, another multiple release system 120 is shown. Theocclusion elements 6 have coils 122 with a hub 124 mounted to each end.The coils 122 and hub 124 are embedded in the dissolvable material 10 toform a dissolvable connection 125 between each of the elements 6. Inanother aspect of the invention, different fluids may be used todissolve each of the connections 125 between the occlusion elements 6.In this manner, premature release of one or more of the elements 6 orpremature degradation of the material 10 is reduced. For example, the pHmay be varied to preferentially dissolve the connections 125 one at atime with each of the connections being dissolved by a different pHfluid.

Referring to FIGS. 37 and 38, another system 127 for releasing theocclusion element 6 is shown. The occlusion element 6 has a portion 128embedded in the dissolvable material. The portion 128 preferablyincludes a flexible filament 130, such as suture, which is attached tothe element 6. The filament 130 may be one or more filaments 130extending somewhat independently similar to FIGS. 11-14 or may form awound, woven or braided structure. The fluid is delivered through alumen 129 to dissolve the material and release the occlusion element 6as shown in FIG. 38.

Referring to FIGS. 39 and 40, still another system 131 for releasing theocclusion element 6 is shown. The occlusion element has an embeddedportion 134 which is embedded in the dissolvable material. The embeddedportion 134 is also preloaded under tension but could also be preloadedunder compression. The portion may be any suitable structure such as afirst coil 136 attached to a second coil 138. The first coil 136 isrelatively flexible and stretches to the expanded position of FIG. 39while the second coil 138 is stiffer and expands less. When released,the embedded or preloaded portion 134 moves to the position shown inFIG. 40. The embedded portion 134 moves into the occlusion element 6,and specifically within the coils, so that the embedded portion does notprotrude from the coil a significant distance when deployed.

Referring to FIGS. 41 and 42, another system 135 for releasing anocclusion element 6 is shown. The system has a delivery element 140having an extension 142 which extends into the occlusion element 6 and,in particular, inside a cavity 144 such as the windings of the occlusionelement 6. In this manner, the delivery element 140 protects thedissolvable material and acts like a blocking element in the mannerdescribed herein. The extension 142 also helps to reinforce the areaaround the dissolvable material 10 to prevent mechanical disturbance ofthe dissolvable material 10 when the catheter is bent or twisted duringadvancement. A tube or stylet 144 may be positioned in the deliveryelement to improve column strength during delivery. Fluid is deliveredthrough the lumen 146 to dissolve the material at the desired time. Thefluid flows out of the extension 142 and into contact with dissolvablematerial 10. The delivery element, like any of the delivery elements orcatheters described herein, may have increased flexibility toward thedistal end as is known in the art.

The present invention has been described in connection with thepreferred embodiments, however, many variations and alternativeembodiments fall within the scope of the invention. For example, theocclusion element may have any shape and may be made of any material.Furthermore, although it is preferred to deliver the fluid to thedissolvable material, the material may also be dissolved by simplycoming into contact with the patient's blood without departing fromvarious aspects of the invention. The dissolvable material maycompletely detach the occlusion element from the delivery element or mayrequire another action, such as withdrawal of the delivery element, tofully release the occlusion element. Finally, the methods and devices ofthe present invention may be used with any medical device and notnecessarily the occlusion elements described herein and use with anysuitable medical device falls within the scope of the invention so thatthe term medical device or element may be substituted for occlusionelement or device as used herein. Thus, the description of the preferredembodiments should not limit the invention. The invention has beendescribed in connection with a number of different features, aspects andadvantages which should be considered independently and, thus, no singleaspect or advantage of the invention should be considered an essentialelement of the invention. For example, various aspects of the inventionmay be practiced with or without various aspects such as the blockingelement, sheath, or fluid circulation.

1. A method of delivering an occlusion element, comprising the steps of:providing an occlusion element which is coupled to a delivery elementwith a dissolvable material, the dissolvable material being dissolvablewith a fluid, the dissolvable material forming a dissolvable connectionbetween the delivery element and the occlusion element; advancing theocclusion element through a patient's vascular system with the occlusionelement coupled to the delivery element with at least the dissolvableconnection; and dissolving the dissolvable material thereby releasingthe occlusion element from the dissolvable connection with the deliveryelement.
 2. The method of claim 1, wherein: the dissolving step iscarried out with the dissolvable material being dissolved faster by thefluid as compared to other fluids contacting the material during theadvancing step.
 3. The method of claim 1, wherein: the providing step iscarried out with the dissolvable material dissolving faster at aselected pH as compared to a pH of other fluids which the materialcontacts during the advancing step; and the dissolving step is carriedout by delivering a fluid having the selected pH to dissolve thedissolvable material.
 4. The method of claim 1, wherein: the dissolvingstep is carried out with the dissolvable material and fluid being asolute and solvent.
 5. The method of claim 1, wherein: the dissolvingstep is carried out by delivering a fluid to the dissolvable material,the fluid being an acid..
 6. The method of claim 1, wherein: thedissolving step is carried out by delivering a fluid to the dissolvablematerial, the fluid being a base.
 7. The method of claim 5, wherein thedissolvable material includes a material selected from the groupconsisting of zinc and iron.
 8. The method of claim 1, wherein thedissolvable material is a polymer.
 9. The method of claim 9, wherein thedissolvable material is a natural polymer.
 10. The method of claim 9,wherein the dissolvable material is an alginate.
 11. The method of claim9, wherein the dissolvable material is a cross-linked polymer.
 12. Themethod of claim 11, wherein the dissolving step is carried out bydelivering a fluid including a cation which dissolves the cross-linkedpolymer.
 13. The method of claim 8, wherein the polymer is in the formof polymer layers bonded together.
 14. The method of claim 13, whereinthe polymer is an acrylic polymer.
 15. The method of claim 15, whereinthe polymer is a methacrylate polymer.
 16. The method of claim 13,wherein the dissolving step is carried out by delivering a fluid havinga pH different than blood.
 17. The method of claim 13, wherein thedissolving step is carried out by using a fluid having a salinitydifferent than blood.
 18. The method of claim 17, wherein the dissolvingstep is carried out with the fluid having a pH of 4-6.5.
 19. The methodof claim 17, wherein the dissolving step is carried out with the fluidhaving a pH of 8-95.
 20. The method of claim 17, wherein the dissolvingstep is carried out with the fluid having a pH of less than 7.0.
 21. Themethod of claim 17, wherein the dissolving step is carried out with thefluid having a pH of greater than 7.4.
 22. The method of claim 1,further comprising the step of: changing a temperature of thedissolvable material during the dissolving step.
 23. The method of claim22, wherein: the temperature changing step is carried out by deliveringthe fluid at a temperature which changes the temperature of thedissolvable material.
 24. The method of claim 22, wherein: thetemperature changing step is carried out by directly heating thedissolvable bond.
 25. The method of claim 24, wherein: the temperaturechanging step is carried out by using resistive heating.
 26. The methodof claim 1, wherein: the dissolving step is carried out by deliveringthe fluid to the material to dissolve the dissolvable material.
 27. Themethod of claim 26, wherein: the dissolving step is carried out with thefluid being delivered through the delivery element.
 28. The method ofclaim 27, wherein: the dissolving step is carried out with a tubepositioned in the delivery element, the tube having a lumen, the tubeand delivery element defining a space therebetween, the fluid beingdelivered through one of the lumen and the space and the fluid beingwithdrawn through the other of the lumen and the space.
 29. The methodof claim 1, wherein: the providing step is carried out with theocclusion element forming coils.
 30. The method of claim 1, wherein: theproviding step is carried out with the dissolvable material having acavity.
 31. The method of claim 30, wherein: the providing step iscarried out with the cavity being a throughhole.
 32. The method of claim1, further comprising the step of: positioning a blocking element toimpede fluid contact with a least a protected portion of the dissolvablematerial, the blocking element being movable to a position spaced apartfrom the protected portion of the dissolvable material.
 33. The methodof claim 32, wherein: the blocking element is positioned in a cavity inthe dissolvable material.
 34. The method of claim 33, wherein: theproviding step is carried out with the blocking element being a tube;and the method further comprising the step of retracting the tube toexpose at least part of the dissolvable material.
 35. The method ofclaim 33, wherein: the providing step is carried out with the blockingelement being a tube; and the dissolving step being carried out with thefluid passing through the tube.
 36. The method of claim 1, wherein: theproviding step is carried out with a flexible sheath extending over thedissolvable material, the flexible sheath being attached to the deliveryelement.
 37. The method of claim 1, wherein: the providing step iscarried out with the occlusion element having a portion embedded in thedissolvable material.
 38. The method of claim 37, wherein: the providingstep is carried out with the embedded portion being embedded in thedissolvable material in an expanded position, the embedded portion beingnaturally biased toward a collapsed position; and the dissolving step iscarried out so that the portion of the occlusion element is no longerembedded in the material thereby permitting the portion to move towardthe collapsed position.
 39. The method of claim 37, wherein: theproviding step is carried out with the portion embedded in the materialincluding a plurality of filaments.
 40. The method of claim 37, wherein:the providing step is carried out with the portion embedded in thedissolvable material being a coil.
 41. The method of claim 1, wherein:the providing step is carried out with the occlusion element having aplurality of flexible fibers embedded in the dissolvable material. 42.The method of claim 1, wherein: the providing step is carried out withthe portion embedded in the material including a ball.
 43. The method ofclaim 1, wherein: the providing step is carried out with the portionembedded in the material including a cage.
 44. The method of claim 1,wherein: the providing step is carried out with a flexible sheathcovering at least a portion of the dissolvable material.
 45. The methodof claim 44, wherein: the providing step is carried out with the sheathhaving openings therein.
 46. The method of claim 45, wherein: theproviding step is carried out with the delivery element having a fluiddistributing portion with openings for distributing the fluid; thedissolving step being carried out to deliver the fluid through theopenings in the distributing portion to dissolve the material.
 47. Themethod of claim 46, wherein: the providing step is carried out with thedistributing portion being conical.
 48. The method of claim 1, furthercomprising the step of: moving the delivery element relative to theocclusion element after the dissolving step to fully release theocclusion element from the delivery element.
 49. The method of claim 1,wherein: the dissolving step fully releases the occlusion element fromthe delivery element.
 50. The method of claim 1, wherein: the providingstep is carried out with the occlusion element having a blocking portionwhich isolates the material from the patient's blood; the advancing stepbeing carried out so that the blocking portion isolates the materialfrom the patient's blood during the advancing step.
 51. The method ofclaim 50, wherein: the providing step is carried out with the blockingportion being a plug of material.
 52. The method of claim 51, wherein:the providing step is carried out with the plug of material beingsolder.
 53. The method of claim 50, wherein: the providing step iscarried out with the blocking portion being a disc.
 54. The method ofclaim 1, wherein: the dissolving step is carried out with the fluidbeing a fluid selected from the group consisting of water, saline andthe patient's own blood.
 55. The method of claim 1, wherein: theproviding step is carried out with the material being selected from thegroup consisting of sugar, salt, mannitol or a combination thereof. 56.The method of claim 1, wherein: the providing step is carried out withthe delivery element having a plurality of occlusion elements; and thedissolving step is carried out a number of times to sequentially releasethe plurality of occlusion elements.
 57. The method of claim 56,wherein: the providing step is carried out with the delivery elementincluding a tube in which the plurality of occlusion elements ispositioned; the dissolving step being carried out by moving the tuberelative to the occlusion elements to expose the dissolvable material tothe fluid.
 58. The method of claim 57, wherein; the providing step iscarried out with the tube having openings therein through which thefluid passes to contact the dissolvable material.
 59. The method ofclaim 58, wherein: the providing step is carried out with the deliveryelement having an outer tube positioned around the tube; and thedissolving step is carried out by delivering the fluid through a lumenpositioned between the tube and outer tube.
 60. The method of claim 59,wherein: the dissolving step is carried out by withdrawing the fluid anddissolved parts of the dissolvable material through another lumenbetween the tube and outer tube.
 61. The method of claim 55, wherein:the dissolving step is carried out by using a first fluid to dissolveone of the dissolvable connections and a second fluid, different thanthe first fluid, to dissolve another of the dissolvable connections. 62.The method of claim 1, further comprising the step of: detecting whetherthe occlusion element has been released from the delivery element. 63.The method of claim 62, wherein: the detecting step is carried out byapplying energy to the delivery element and detecting a change in aparameter thereby indicating release of the occlusion element.
 64. Themethod of claim 63, wherein: the detecting step is carried out byapplying RF energy.
 65. The method of claim 64, wherein: the detectingstep is carried out with the parameter being the standing wave ratio.66. A system for delivering a medical device to a patient, comprising: adelivery element; and a medical device coupled to the delivery elementwith a dissolvable material, the dissolvable material forming adissolvable connection between the medical device and the deliveryelement, the dissolvable material being dissolvable with a fluid. 67.The system of claim 66, wherein: the medical device is an occlusionelement for occluding a vascular region.
 68. The system of claim 67,wherein: the delivery element has a lumen.
 69. The system of claim 68,further comprising: a fluid source coupled to the lumen.
 70. The systemof claim 69, wherein: the fluid source contains a fluid selected fromthe group of fluids consisting of the patient's own blood, water,saline, and combinations thereof.
 71. The system of claim 66, wherein:the material is selected from the group of materials consisting ofsugar, mannitol, salt and combinations thereof.
 72. The system of claim66, wherein: the dissolvable material has a cavity.
 73. The system ofclaim 72, wherein: the cavity has a throughhole.
 74. The system of claim66, further comprising: a blocking element positioned to impede fluidcontact with a least a protected portion of the dissolvable material,the blocking element being movable to a position spaced apart from theprotected portion of the dissolvable material to permit dissolution ofthe protected portion
 75. The system of claim 74, wherein: the blockingelement is positioned in a cavity in the dissolvable material.
 76. Thesystem of claim 75, wherein: the blocking portion is a tube positionedin the cavity.
 77. The system of claim 66, wherein: the medical devicehas an embedded portion which is embedded in the dissolvable material.78. The system of claim 77, wherein: the embedded portion is embedded inthe dissolvable material in an expanded position, the embedded portionbeing naturally biased toward a collapsed position after dissolution ofthe dissolvable material.
 79. The system of claim 77, wherein: theportion of the delivery element embedded in the material has a pluralityof filaments.
 80. The system of claim 77, wherein: the portion embeddedin the dissolvable material is a coil.
 81. The system of claim 66,further comprising: a flexible sheath covering at least a portion of thedissolvable material.
 82. The system of claim 81, wherein: the sheathhas openings therein.
 83. The system of claim 66, wherein: the deliveryelement has a fluid distributing portion with openings for distributingthe fluid.
 84. The system of claim 83, wherein: the distributing portionis conical.
 85. The system of claim 66, wherein: the medical element hasa blocking portion which protects the material from exposure to fluidoutside the delivery device.
 86. The system of claim 66, wherein: theblocking portion is a plug of material.
 87. The system of claim 86,wherein: the plug of material is solder.
 88. The system of claim 66,further comprising: a catheter having a lumen; the delivery elementbeing a wire; the medical device being mounted to the wire with thedissolvable material.
 89. The system of claim 88, further comprising: asource of fluid coupled to the lumen, the fluid dissolving the material.90. The system of claim 66, wherein: the delivery element has a helicalelement; the helical element contacting the dissolvable material toenhance the bond between the delivery element and the material.
 91. Thesystem of claim 66, wherein: the delivery element has a textured surfacewhich contacts the dissolvable material.
 92. The system of claim 66,wherein: the delivery element has a preloaded portion which exerts aforce on at least one of the dissolvable material and the medicaldevice.
 93. The system of claim 92, wherein: the preloaded portion iscompressed in a loaded position and is expanded when in a releasedposition.
 94. The system of claim 92, wherein: the preloaded portion isradiopaque.
 95. The system of claim 94, wherein: the preloaded portionhas a exposed portion which is exposed in the loaded position, theexposed portion moving inside the medical device when moving to thereleased position.
 96. The system of claim 95, wherein: the exposedportion is embedded in the dissolvable material, the dissolvablematerial being attached to the delivery element.
 97. The system of claim94, wherein: the preloaded portion includes a spring.
 98. The system ofclaim 66, wherein: the medical device has a preloaded portion whichexerts a force on at least one of the material and delivery element. 99.The system of claim 98, wherein: the medical device is an occlusionelement having coils which are in an expanded shape when embedded in thematerial and which collapse when the material is dissolved.
 100. Thesystem of claim 66, further comprising: means for heating the materialto enhance dissolution of the material.
 101. The system of claim 100,wherein: the heating means uses electrical energy and is a resistiveheater.
 102. The system of claim 66, wherein: a number of medicaldevices are mounted to the delivery element.
 103. The system of claim102, wherein: a dissolvable connection is provided between each of themedical devices
 104. The system of claim 103, wherein: at least two ofthe dissolvable connections are dissolved with different fluids.
 105. Amethod of delivering a medical device, comprising the steps of:providing a medical device which is coupled to a delivery element with adissolvable material, the dissolvable material being dissolvable with afluid, the dissolvable material forming a dissolvable bond between thedelivery element and the medical device; advancing the medical deviceinto a patient with the medical device coupled to the delivery element;and dissolving the dissolvable material thereby releasing the medicaldevice from the delivery element.